Difficulty with multiple overlaying textures on one material
There are several choices to make multiples bumps on one object.


Make it via the different shaders.
Not relevant in your case because Chocofur fabric shaders don't have input for normals/bumps, so you would need to modify all shaders.
Make it via different materials.
Would need more work at this step.
Make it in the material by combining several bumps maps.
The picture explain it well I think: